Simplify GUI settings and build flags

internal/common/project_paths.go

@@ -5,6 +5,8 @@ import (
 	"path/filepath"
 )
 
+var rootDirFunc = RuntimeBaseDir
+
 func RuntimeBaseDir() string {
 	exe, err := os.Executable()
 	if err == nil {
@@ -13,4 +15,12 @@ func RuntimeBaseDir() string {
 	return "."
 }
 
-func RootDir() string { return RuntimeBaseDir() }
+func RootDir() string { return rootDirFunc() }
+
+func SetRootDirForTest(fn func() string) func() {
+	prev := rootDirFunc
+	rootDirFunc = fn
+	return func() {
+		rootDirFunc = prev
+	}
+}